FXUS61 KCLE 010221 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1021 PM EDT Wed Apr 30 2025 .SYNOPSIS... Another low pressure system is headed for the southern Great Lakes tonight with a warm front pushing through, followed by a cold front Thursday and more thunderstorm potential. An upper level cutoff low with cooler weather moves in for the weekend. && .NEAR TERM /THROUGH THURSDAY NIGHT/... 10:15 PM Update: No notable changes to the forecast through Thursday. Massaged the timing of higher shower/storm chances a bit in the grids. Showers falling out of a mid-level deck produced a few sprinkles at the ground in Northwest OH this evening, though are now shifting east over Lake Erie. Scattered showers, and perhaps an elevated storm or two, will arc northeast across the area just ahead of a warm front overnight tonight into early Thursday. We will then get into the open warm sector on Thursday, and should see a few hours of mainly dry weather (outside of a lingering isolated shower or two) with at least breaks of sun. The main focus Thursday afternoon and early evening then shifts to potential for convection to develop along/ahead of a cold front approaching from the west. Most regional and hi-res models suggest a pre-frontal trough or two progressing east across our area through the afternoon and early evening, and these are expected to be the primary foci for convective development in the afternoon. The cold front pushes in from the west Thursday evening, with a weakening line of convection potentially accompanying it. Some disagreement regarding the amount of heating along with the placement for those more subtle pre- frontal troughs leads to uncertainty regarding the specifics regarding the convective evolution and severe threat. However, despite somewhat limited heating and poor mid-level lapse rates, it seems that 750-1500 J/KG of MLCAPE should develop during the afternoon in a moderately sheared (35-45kt of deep-layer shear) environment. This does support organized convection with some severe threat if we see any supercells early in the convective cycle (most likely from far eastern OH into PA where low-level flow may remain more backed into the afternoon), or if we see upscale growth into lines or clusters...with enough 0-3km shear to support an embedded bow or two with any upscale growing clusters. While uncertainty remains, stay tuned for updates. Previous Discussion: The active pattern will continue despite a day of drying with cooler air and low dewpoints. Warm front to cross the CWA border southwest to northeast late tonight with an expected cluster of showers and isolated thunder within. The instability above a steep surface inversion is not favorable for thunder but cannot eliminate the potential based on forced ascent as there will exist very modest CAPE around 700mb. The surface low of this low pressure system will track also from southwest to northeast from central Illinois towards Lake Huron, west of our CWA boundary. Will be in the warm sector for a short period of time early Thursday into the afternoon/evening hours. Small areas of PVA within the southwest 500mb flow/height gradient will necessitate the need for low end POPs while in the warm sector residence time. Main line of convection is going to form ahead of the cold front with main initiation time of after 16Z. Far western zones may not see this activity as the progress of the cold front may be through that area before cells/line develops. As far as the severe potential goes, there could be a concern with the antecedent cloud cover and showers working to inhibit strength through CAPE, but the convection itself will not rely on thermodynamics to get going and should have enough shear to organize it. Expecting gusty winds and cannot eliminate a hail threat, but with the surface winds veering ahead of the front the tornado risk decreases, but again, non-zero. In the end, the severe threat is highest for the eastern two-thirds of the CWA. The yo yo-ing of temperatures continues, and after a day highly influenced by the ENE winds off Lake Erie and temperatures in the upper 40s to mid 50s, with 60s in the southern CWA, upper 70s to around 80F is possible in the warm sector prior to the line of convection/cold front. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Aloft, SW'erly cyclonic flow and embedded/subtle shortwave disturbances affect our region through Saturday as a prominent trough axis shifts SE'ward from the northwestern Great Lakes and central Great Plains to near Lake Huron and the Lower OH Valley, when an embedded mid/upper-level low should develop near the IL/IN border area. At the surface, a front should waver just west and north of Lake Erie through Friday afternoon as one frontal low moves ENE'ward across southeastern ON, north of Lake Ontario, and southern QC, and a separate frontal low moves from the southwestern Great Lakes toward southern Lake Huron. The front should sweep SE'ward as a cold front across Lake Erie and our CWA Friday evening through Friday night as the second aforementioned frontal low moves farther ENE'ward toward the Upper Saint Lawrence River Valley. Behind the cold front, a trough is expected to linger over the Lake Erie region and Upper OH Valley. Peeks of sunshine and low-level warm/moist air advection from the Gulf are expected to allow late afternoon highs to reach the 60's to lower 70's on Friday. Low-level CAA behind the cold front should contribute to Friday night's lows reaching the upper 40's to lower 50's around daybreak Saturday. Despite peeks of sunshine on Saturday, continued low-level CAA is expected to limit late afternoon highs to the mid 50's to lower 60's in our CWA. Scattered showers and thunderstorms should occur along and ahead of the cold front Friday into Friday night as low-level convergence/moist ascent along the front and surface trough axes accompanying the aforementioned shortwave disturbances release surface-based and elevated CAPE, and moist isentropic ascent ahead of the shortwave trough axes releases elevated CAPE. Instability is expected to be mainly weak, but limited daytime heating of the warm/moist sector boundary layer may yield moderate surface-based CAPE Friday afternoon through early evening. Showers/storms should produce periods of heavy rain amidst unusually-high PWAT values in the warm/moist sector. Some storms may be strong to severe amidst moderate to strong deep-layer bulk shear. SW'erly mean mid-level flow around 40 to 50 knots is expected to allow showers/storms to train along the front, but fast shower/storm motions should limit flash flood potential. Behind the front, additional and scattered rain showers are expected Friday night through Saturday courtesy of moist isentropic ascent ahead of the prominent trough axis aloft. During Saturday night, SW'erly flow aloft, over our CWA, should back to S'erly to SE'erly as the trough aloft settles SE'ward over our region and the embedded mid/upper-level low drifts SE'ward from near the IL/IN border area toward the Mid OH Valley. Scattered rain showers should continue to impact our region as the low pressure system's warm conveyor belt undergoes moist isentropic ascent aloft. At the surface, a trough should linger over/near our CWA. Lows should reach the 40's around daybreak Sunday as low-level CAA persists across our region. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The latest consensus of NWP model guidance indicates troughing at the surface and aloft should continue to impact the Lake Erie region and Upper OH Valley during the long-term period. Simultaneously, the mid/upper-level low mentioned in the short-term forecast discussion should wobble near the Mid OH Valley through Tuesday before moving ENE'ward toward NJ and vicinity on Wednesday as a downstream blocking ridge aloft over the northwestern Atlantic begins to weaken. Periodic and scattered rain showers are expected on Sunday through Wednesday, respectively, due to the following: the low pressure system's warm conveyor belt undergoing moist isentropic ascent aloft; low-level convergence/moist ascent along surface trough axes expected to accompany shortwave disturbances that should revolve around the mid/upper-level low. The best potential for showers should exist each late morning through early evening due to the expectation of a typical diurnal cycle in surface air temperatures/boundary layer stability (e.g. weak diurnal destabilization of a moist boundary layer). The low-level convergence/moist ascent along the aforementioned surface trough axes may release sufficient boundary layer CAPE to trigger a few late afternoon and early evening thunderstorms, especially on Monday through Wednesday, respectively. A gradual moderating trend in surface air temperatures is expected during the long-term period as low-level temperature advection amidst the slow-moving low pressure system's cyclonic circulation eventually allows relatively-warmer air to overspread our region from the north and west as north-south baroclinicity decreases and cloud cover decreases gradually. Late afternoon highs in the mid 50's to mid 60's on Sunday and the 60's to lower 70's on Monday should moderate to late afternoon highs reaching the mid 60's to mid 70's on Tuesday and Wednesday, respectively. Lows should reach the lower 40's to lower 50's around daybreak Monday and Tuesday, respectively, and the upper 40's to mid 50's around daybreak Wednesday. && .AVIATION /00Z Thursday THROUGH Monday/... VFR is observed across the board this evening. A deck of mid- level clouds is producing some showers across Northwest OH... these are mainly not reaching the ground so only included VCSH at TOL. A warm front lifts northeast across the area overnight tonight and early Thursday. Scattered showers will likely accompany this feature. Any restrictions would be brief, though there will be some elevated instability so an isolated heavier shower or storm is possible. Generally handled with VCSH mentions, with some PROB30 groups for brief reduced visibility and/or TS where potential for this appears higher. We get into the warm sector ahead of an approaching cold front Thursday morning and early afternoon. This cold front begins pushing in from the west towards Thursday evening. While isolated shower potential can't be ruled out in the open warm sector, a few hours of mainly dry weather with some breaks in the clouds is likely. Storm potential ramps up ahead of the cold front through the afternoon and early evening on Thursday. Confidence in impacts is rather high from CLE-MFD points east, though confidence is a bit lower at TOL and FDY. Thunderstorms in the afternoon will be capable of brief vsby and ceiling restrictions, along with gusty winds locally to 40kt or more. Storms will generally move to the northeast at ~40kt. Winds will be light out of the east to southeast tonight. Winds shift south-southwest into Thursday and increase to 12-20kt sustained with gusts 25-30kt common by the afternoon. Outlook...Non-VFR potential with showers/storms lingers into Thursday night. Non-VFR may linger across the eastern half of the area into Saturday. && .MARINE... Onshore winds around 5 to 10 knots, associated with a lake breeze through this early evening, give way to NE'erly to SE'erly winds around 5 to 15 knots tonight as a ridge begins to exit toward New England. Waves of 3 feet or less are expected. On Thursday through Friday night, a low should move NE'ward from the Mid MS Valley toward the mouth of the Saint Lawrence River. Accordingly, a warm front should drift N'ward across Lake Erie on Thursday and allow NE'erly to SE'erly winds around 10 to nearly 20 knots to veer to S'erly to SW'erly. Waves remain mainly 3 feet or less in U.S. waters, but occasional 4 footers are expected in open U.S. waters. Behind the warm front, SW'erly winds around 10 to 15 knots persist before a cold front sweeps SE'ward across Lake Erie Friday evening through Friday night and causes winds around 10 to 15 knots to veer to NW'erly. Waves of mainly 3 feet or less should persist, but occasional 4 footers are possible. We will monitor forecast trends for the potential need for a Small Craft Advisory. Behind the cold front, a trough should linger over Lake Erie through this weekend and Monday as a ridge attempts to build from the north- central United States. NW'erly winds around 10 to 15 knots should veer gradually to E'erly. Waves of 3 feet or less are forecast. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...26 NEAR TERM...26/Sullivan SHORT TERM...Jaszka LONG TERM...Jaszka AVIATION...Sullivan MARINE...Jaszka